Mercury switch



May 12, 1942 H. BucKLEN ETAL 2,282,512

MERCURY SWITCH Filed April 2o, 1940 4 sheets-'sheet 1 30.272529/2 23/7/3 L, WJ 33 A x ,0

Q7' C ws 32 INVENTORS.-

ATTORNEY.

May 12,v 1942- HEBUQKLEN Em., I 2,282,512

MERCURY SWITCH Filed April 20, 1940 4 SheelZS--Sheei'l 2 ATTORNEY.

May 12,1942. H. E. BUCKLEN E1- A1.

MERCURY SWITCH Filed April 20, 1940 4 Sheets-Sheet 3 INVENTORS Jerberi Zzzc/ElefU/k BY UQ@ ecin.

u MKM ATTORNEY.

May l2, i942. H. E. BucKLEN E1- AL MERCURY SWITCH Filed April 20, 1940 4 SheetS-SheetI 4 aww. @www mme@ m5. A @of z ,ww

Patented May 12, 1942 UNETE STATESA PATENT orti MERCURY SWITCH Herbert El Bucklen and Uno C. Hedin, Elkhart, A Ind., assignors to Bucklen-Bear Laboratories, Inc., Elkhart, Ind., a corporation of Indiana Application April zo, 1940, serial No. 330,654

13 claims. (ci. zoo-152) This invention relates to mercury switches of the metal envelope type, and is directed more particularly to an improvement in such switches over the type shown in the patent to Paul S. Bear, No. 2,132,921, issued October 11, 1938.

In previous types of mercury switches of the metal envelope type in which a ceramic insert is provided at one end for supporting an electrode in insulated relation to the metal shell it has sometimes been found desirable to provide for retaining a body of mercury in contact with the electrode in order to secure a mercury to mercury contact within the envelope. However, in all of the constructions with which we are familiar, it appears that, under certain conditions, the apparent mercury to mercury contact is in reality a metal to mercuryV contact due to the fact that rapid tilting ofthe switch causes the movable body of mercury to impinge directly upon the electrode face, thus producing arcing between the metal and the mercury. A metal to mercury contact switch of this type, according to tests we have conducted, has only about onefourth of the normal life of a switch embodying a mercury to mercury contact.

The present invention has for its primary bject` the provision of a switch construction in which the retained and movable bodies of mercury are in nearly equalized volume so that inV effect a double run of the mercury is provided upon tilting of the .switch in either direction; The term double run mercury is coined from the fact that the mercury now runs in two directions simultaneously at the instant of make or break in the switch. Switches of the type heretofore known Vmight be called single run switches, since the retained body of mercury was held substantially stationary andthe balance of the mercury was caused to part therefrom and run down an inclined spillway for breaking the circuit.

In designing the structure so that mercury to mercury conta-ct is insured, about 25% to 50% of the total mercury volume should be retained in contact with the iixed electrode and the remaining portion of the mercury allowed to move upon tilting of the switch in contact with the switch envelope. With such a construction providing a relatively large well for the retained body of mercury, upon tilting of the switch toward switch closed position the retained body moves simultaneously with the movable body and blanks off the electrode face so that the leading edge of the movable body is prevented from contacting directly with the electrode but instead, contacts the moving portion of the retained body which at this time overlies the electrode face. As a result, positiver mercury to mercury contact is provided in the switch.

Similarly, when the switch is in switch closed position, tilting of the switch toward switch open position results in both bodies of mercury moving simultaneously away from the switch closed position with the two bodies being separated iover the ceramic barrier at a point removed from the electrode face, one of the bodies running down into the well adjacent the electrode, while the other body moves down into the main portion of the switch envelope. Due to this simul- ,.taneous movement of both bodies in both making and breaking operations, it is apparent that a. snap action or increased rapidity of contact will be provided as well as an increased rate of separation, since velocities of the two bodies are a cumulative. As a result, even if the switch is used-in response to a slow moving actuator such as a thermostat or the like, the velocities of the body due to the double run feature willprevent any appreciable arcing, either upon making or Abreaking of contact.

By providing the increased volume of mercury in the retaining well approximately one-fourth of the total mercury volume in the switch, and in some-cases being substantially one-half of this Volume, a cooler operating switch is provided.

Still another feature of the present invention is to designa switch construction in which the point of making and breaking of the circuit is produced over a ceramic or insulating surface appreciably removed from the electrode face,

which insures a cool operating switch and prevents any possibility of arcing on the adjacent metal.

Still another feature of the present invention 4501 is the design of the structure so as to provide for rapid dissipation of heat from the interior of the switch. This may be produced by forming the envelope in such manner that air circulation is provided adjacent all portions of the ceramic and by insuring that the point at which the two bodies of mercury make and break contact is removed from both electrodes.

Another feature involved in the present design M part by a skirted portion of the electrode to increase the area of contact between the body of mercury and the electrode, thereby reducing the internal resistance through the switch.

Still another feature of the present invention is.the provision of a ceramic designed with due regard for the fact that mercury bodies retain their stability only when confined within an opening of 37g" or less. Employing this characteristic, the ceramic in one form of the present invention is so designed as to provide a substantially fixed retained body of mercury in contact with the electrode, but so arranged that the movable body of mercury will at no time have any opportunity to contact the face of the elecN trode directly, but will contact stabilizedV portions of the retained body prior to moving into proxlmity to the electrode. As a r,esult,.such a switch has a very stable action and can be used for high speed operation without any danger of double or secondary contacts. 1n connection with this, the area of contact between the retained body and the electrode is materially increasedV to insure low internal resistance, and consequently cool operation of the switch.

Another advantage derived by the present invention resides inthe forming of an electrode structure in which the retained body of mercury is in contact with an appreciable area thereof but the electrode face is shielded against any possible contact from the movable body of mercury, positively insuring a mercury to mercury contact. This shielding may be produced by covering the radial portion of the electrode which faces the opening in the ceramic with a suitable insulating medium or in any other suitable manner.

Still another advantage secured by the present invention is the design of a switch having a straight cylindrical bore inthe ceramic and provided with a radially extending shoulder or abutment at the envelope end of this bore whereby the movable body builds up and substantially breaks across the space into contact with the retained body. This provides a rapid contact insuring little or no arcing betwen the two bodies even with relatively slow tilting of the switch, since the surface tension of the mercury prevents the contact until a sufficient head has been built up by the dam to insure the movable mercury breaking rapidly across the ceramic surface.

Still another object of the present invention is to provide a switch construction in which the face of the electrode is provided with a baille disc composed of a metal which is; arc-resistant and which may be of the group comprising tungsten, molybdenum or tantalum. By facingk the iron electrode face with a metal having a far higher melting point, lower resistance and higher conductivity than that of iron, the iron disc is protected, and at the same time the conductivityA fied structure having the electrode face shielded against contact by the movable body of mercury;

Figures 3 to 6, inclusive, are corresponding views of a further modilied form of switch in various operating positions illustrating the double run characteristics provided by the enlarged volume of mercury retained in contact wtih the electrode;

Figure 7 is acorresponding View of a switch modified to provide additional cooling surfaces;

Figure 8 is a sectional view through a switch havingr a stabilized retained body which is adapted to be contacted by the movable body breaking across a restraining ceramic dam;

Figure 9 is a sectional view taken substantially on line 9-9 of Figure 8;

Figure 10 is a sectional View of a slightly modified form of switch enclosed within an insulating case;

Figure 11 is a sectional view illustrating one manner of sealing the ceramic in the switch end;

Figure 12 is a detail sectional view showing a slightly different manner of shielding the electrode face;

Figure 13 is a sectional view of a modified envelope construction and sealing arrangement for a switch of this type;

Figure 14 is a sectional view through a switch formed from a tubular blank and embodying certain features of the present invention; and

Figure 15 is a sectional view through a still further modied form of switch.

.Referring now in detail to the drawings, in Figure 1 we have disclosed a switch envelope indicated generally at 5 having a relatively elongated tubular portion 6 closed at one end, as indicated at 1, and provided with a reversely turned annular flange portion 8 spaced from'the external periphery of the tubular portion 6 by the gap 9.

From the ange portion 8 the envelope has a radially and axially directed flanged or shouldered portion II) terminating at its outer edge in the enlarged cylindrical flange I2. This switch envelope may be formed by drawing or the like, or in any other suitable manner, and preferably, 1s subjected to a hydrogen annealing process to drive out occluded gases and burn olf impurities before the ceramic I3 is inserted into the anged end thereof. The ceramic I3 is provided with a shoulder portion I4 abutting against the radial flange I!) and provided with an annular groove I5 in the face thereof in which is inserted a resilient sealing ring I6, which ring is compressed against the surface of the flange I IJ to provide an eifective seal preventing leakage between the external surface of the ceramic and the internal surface of the envelope.

The ceramic I3 is provided with radially spaced annular grooves I'I and I8 spaced apart by an ,annular axially extending partition or wall I 9, the grooves I1 and I8 forming a series of undercuts beneath the radially inwardly extending flange portion 20 of the ceramic which is bored, as indicated at 22, to provide an opening from the tubular portion 6 of the envelope into 4the outer end of the ceramic. The annular groove I1 in the ceramic is counterbored to provide a radial shoulder 23 against which is seated the forward edge of the cylindrical ange 24 of a metal electrode 25 disposed in the counterbore and centered with respect to the ceramic thereby. The electrode 25 closes the outer end of the ceramic and, as noted, is spaced an appreciable distance rearwardly of the bore 22 of the ceramic.

The electrode 25 is of disc-like form having the projecting flange 24 forming a cup-shaped recess with the outer end of the ceramic. The electrode is provided with an axially outwardly directed shank 26 adapted to be connected to any suitable current source.

Suitable resilient sealing means 21 engages the radial outer face of the electrode 25 about the shank 26, and is provided with an axially extending peripheral skirt 28 radially overlapping the outer end of the electrode, and also the shouldered portion 29 of the ceramic. The seal 21 is compressed into sealing engagement between the electrode, ceramic and flange I2 by means of an insulating compression member 30 urged into compressive engagement with the seal by means of the retaining flange or ring 32 and the spun-over edge 33 of the envelope. Preferably, the compression member 39 is provided with a cylindrical axial extension 34 forming an insulating separator between the metal retaining ring 32 and the electrode shank to prevent anyA possibility of flash-over therebetween. The compressionproduced by spinning over the end 33 of the envelope also serves to compress the sealing ring I6 providing an adidtional seal adjacent the front or inner portion of the ceramic.

After the ceramic and electrode have been sealed in position, as described above, the envelope is partially filled with mercury through the tubulation 35 at the closed end 1 of the tubular portion 6 of the envelope. The volume of mercury introduced is sucient to form theY retained body 36 and the movable body 31 separated by the radially inwardly flanged portion 20 of the ceramic. It will be apparent that the retained body 36 is of appreciable volume as compared with the body 31 since it fills the lower portions of both of the annular grooves I1 and I8, and also the annular space between the electrode face and the flange 26 of the ceramic. It will be noted that this body of mercury lies in contact with both the electrode face and also with the flange 24 of the electrode for an appreciable part of the circumference thereof, thus providing ample contact area to insure low conductivity therebetween. After the mercury bodies have been introduced into the envelope, the tubulation 35 is subjected to a vacuum for exhausting all air or other gases which may have been trapped in the envelope, and the interior of the envelope is then subjected to a hydrogen atmosphere under pressure. While maintaining the tubulation connected to a source of hydrogen under pressure, the tubulation 35 is pinched flat, as indicated at 38, and this flattened portion is then welded, sealing off the interior of the envelope with the hydrogen retained under pressure therein.

The switch of Figure 1 is adapted for operation by tilting movement, and it will be at once apparent that upon tilting the switch from the position shown in a counter-clockwise direction, the body of mercury 36 being of an appreciable volume will ow upwardly over the face of the electrode 25 at the same time that the body of mercury 31 starts to build up a head againstv the opposite side of the flange 29. This double movement of the mercury insures, first, the protection of the .electrode face against any possibility of a mercury arc, and, secondary, a movement of the two bodies of mercury toward the bore 22, which increases the rapidity of action so that 'as the body of mercury 31 breaks over the lower dening edge of this bore it moves into direct contact with the body of mercury 36, positively insuring a mercury to mercury contact in which the arc will occur somewhere about the defining edge of the bore 22. Similarly, when the n edge of the bo-re 22, and consequently breaking of the circuit will be effected at this dening edge, which is spaced an appreciable distance from the electrode face. Thus, any arcing produced by the breaking of the switch will have no eifect upon the electrode face. Similarly, the body of mercury 31 will protect the tubular portion 6 of the envelope by overlying the same vadjacent the flange 20 against any possibility of arcing therewith.

While the envelope shown in Figure 1 may be formed without the double flanged portion 8 providing the lannular opening 9 with the ceramic, this has been provided for the purpose of allowing air to pass through this annular opening 9 to insure rapid conduction of heat away from the ceramic, thereby Vmaintain-- ing the switch cool and increasing, Yto a great extent, the operating life thereof, as well as insuring positive repeat performance of the switch insofar as its operating angles are concerned.

It should be Iapparent that by designing ya ceramic having the undercuts as defined by the grooves I1 and I8, an appreciably larger volume of mercury can be retained in contact with the .electrode than was heretofore possible, while at the same time, due to the annular shape of the retaining chamber, any tilting movement will result in rapid movement of the mercury body 36 out of the grooves I1 and I9 and up along the face of the electrode 25 to protect this face and shield it against impingement from the mercury body 31.

Considering now the form ofthe invention shown in Figure 2, the metal envelope shell 49 is provided having the cylindrical body portion 42 provided with the integrally closed end 43. The opposite end of the shell is enlarged to form a cylindrical open end portion 44 joined to the body portion 42 by the frusto-'conical shoulder 45. Disposed within the open end of the shell is a ceramic insert 46 having an inclined runway 41 terminating at its small end in a radial wall 48 whichV defines with the cylindrical bore 49 of the insert an annular groove or recess shouldered or counterbored to receive the annular projecting cylindrical flange 59 of an electrode 52. The electrode'52 closes the outer end of the bore 49 of the ceramic, land a suitable tubulation 53 is extended into the electrode and therewith.

is provided with an opening 51 providing communication 'with the interior of the envelope 42. The tubulation 53 is preferably provided with a copper coating or sleeve 58 extending through the bore of the electrode 52 and providing for increased conductivityto provide a terminal connection to the electrode from the projecting end of the tubulation.

Suitable resilient sealing means 68 is adapted to engage the radial ,face ofV the electrode 52 around the sleeve 58 and tubulation 53, and is provided with a skirted portion 62 radially overlapping the electrode and a portion of the ceramic insert 46 to form a radial seal thereabout. The sealing means 66 is compressed into sealing engagement by means of a compression member 63 corresponding to the member 30 of Figure 1 having the reduced cylindrical extension 64 formingv an insulating spacer about the projecting tubulation and sleeve. The compression member is held in position by spinning over the end 65 of the envelope 40 against a metal retaining ring 66.

Disposed within the switch envelope is a retained body of mercury 61 held in the annular groove formed by the radial shoulder 48, the bore 49 and skirt 58 of the electrode, and a movable body of mercury 68 carried in the tubular portion 42 of the envelope and adapted to move over the inclined surface 41 into and out of contact with the body of mercury 61.

Inasmuch as the inner face of the electrode 52 is shielded by the refractory 55, it is apparent that there can be no direct metal to mercury cony tact upon operation of the switch but that a true mercury to mercury contact will be effected at all times. Also, due to the relatively long skirt portion 50 on the electrode, it is obvious that an appreciable contact area is provided between a retained body 61 and the electrode suiiicient to materially reduce the internal resistance of the switch.

The tubulation 53 is provided for introducing the mercury bodies into the switch envelope after which the tubulation is connected to a source of vacuum and the switch chamber is thereby evacuated and then lled with gas such as hydrogen under pressure after which the tubulation is pressed together and sealed as indicated at 69, similar to the manner described in connection with Figure 1. The copper sleeve 58 adds materially to the conductivity of the lead-out connection provided by the tubulation to insure reduction of internal resistance between the electrode and the terminal connection at the outer end of the tubulation. The structure shown provides a switch having a narrow operating angle, and it will be apparent that any arcs caused by making or breaking of the circuit through the switch will occur over the edge dened by the small end of the runway 41, and consequently will be spaced at an appreciable distance from any metal portion of the switch, these metal portions being thoroughly shielded by the mercury bodies so that there is no possibility of a metal to mercury contact. Due to the relatively large volume of mercury 61 in the retained body, it will be apparent that the same double run eiect is produced, and that the two lbodies of mercury move simultaneously upon opening of the circuit away from the sharp cutting edge provided at the inner end of the recess 41 and consequently insure breaking of the circuit at this point.

Considering now thev form of the invention shown in Figures 3 to 6, inclusive, we have provided a switch structureA incorporating the features of double run of the two bodies of mercury combined with the concept of increasing the volume of the retained body to an extent such that it will at all times mask the electrode face to prevent any metal to mercury contact.

In this form of the invention, the two-diameter metal envelope 10 has inserted therein the ceramic insert 12 provided with the radial shoulder portion 13 terminating the small diameter portion of the envelope. The insert is provided with a straight cylindrical bore 14 terminating at its inner end in the radial shoulder 15 and provided with the annular undercut groove 16 which is counterbored to receive the projecting cylindrical extension 11 of the electrode 18. Suitable sealing means 19 is provided for the outer radial face of the electrode 18 and the end of the ceamic, this sealing means radially overlapping a portion of the ceramic by reason of the skirted portion 80. 'Ihe sealing means is retained in position by means of the compression member 82 held in position by the spun-over edge 83 of the envelope.

The envelope 10 is provided with the usual tubulation as previously described, and disposed within the undercut groove 16 and lying in the annular recess formed by this groove, the edge 15 and the base of the electrode, is a retained body of mercury 84 which, as will be apparent, has sufficient volume so that it contacts an appreciable portion of the inner face of the electrode 18. A movable body of mercury B5 is disposed in the tubular portion of the envelope and, r

as indicated in Figure 3, is dammed up against movement through the opening 14 by means of the radial shoulder 13. Upon tilting of the switch in the position shown in Figure 3, the movable body of mercury 85 piles up against the shoulder 13 until such time as a suiiicient head is produced to break the surface tension and allow the upper stratum of the body of mercury 85 to rush through the opening 14 into contact with that portion of the body 84 lying in the opening 14 closing the switch circuit, as indicated in Figure 5. It will be apparent that by the time this occurs, the retained body 84 has moved over a sufficient portion of the face of the electrode 18 that no portion of the body 85 can contact the electrode portion 18, but a pure mercury to mercury contact is effected. From the position shown in Figure 5 the switch may be opened by tilting in the'reverse direction, as indicated in Figure 4, causing the movable body of mercury 85 to move outwardly through the opening 14 at the same time that the retained body 84 is moving down into the well formed by the undercut 16 inv the insert. As the two 4bodies of mercury tend to separate over the edge 15, the movable body 85 tends to move down into the closed end of the envelope, while the retained body 84 piles up in the Well provided by the undercut and in the annular space between the edge 15 and the electrode face. Inasmuch as the undercut is annular in form, an appreciable volume of the mercury body 84 moves into the undercut, as indicated by the dotted line 86, showing the level of the mercury around the bore 14 within the undercut.

It is apparent therefore that with this type of switch, the two bodies of mercury both tend to move away from each other upon tilting of the switch toward open position, and the separation is eiected about the edge 15 with both bodies moving away from this edge. As a result, a

double run action is provided, insuring positive breaking of the mercury circuit at a point removed from any metal portion ofthe switch structure. The provision of the radial shoulder 13 on the ceramic is of importance in insuring rapid movement of the movable body 85 through the bore 14 only after a predetermined mercury head has been built up, thus providing for a positive and snappy closing of the circuit, and eliminating any thin tongue of mercury running through the opening of insulcient section to carry the desired current. Preferably, the ce'- -ramic is provided with the externally carried seal 81 bearing against the shouldered portion of the envelope for preventing any portion of the mercury body 85 moving between the insert and the envelope wall. It will be apparent that with this construction, the bodies of mercury 84 and 85 approach equality, and that the volume of the body 84 is more than suf-cient to shield the electrode face against any possibility of direct impingement thereon of the body 85.

In the embodiment of the invention shown in Figure '1, which is a combination of the features shown in Figures 2 and 3, the metal envelope 90 is provided with the enlarged cylindrical end portion 92 receiving the ceramic insert 93, this insert having the radial shoulder portion 94 and the annular undercut groove 95 defining an annular well with the flange portion 96 of the electrode 91. The electrode 91 is provided with suitable tubulation 98 for filling and evacuating the switch envelope, which tubulation is provided with a copper sleeve as described in connection with Figure 2. Sealing means 19 and 82 correof Figure 3. In this form of the invention the ceramic I I0 is of generally cylindrical form having a frusto-conical inner portion H2 engaging the inner portion of the shoulder of the shell 10.

wardly extending nger portions` H0. Preferably, four of such ngers are provided which extend toa point approximately Afrom the inner face of the electrode H8, as indicated by the dimension a; also the circumferential spacing between the fingers is approximately as indicated by the dimension b. The purpose of this spacing is to provide a stable retained body of mercury since. we have found that a body of mercury confined within a cap of gli" or less possesses spending to that shown in Figure 3 is provided for the purpose of sealing the outer end of the envelope.

The opposite end of the envelope is provided with a tubular shell portion 99 having the reentrant central cup portion |00 dening an axial recess |02 in the end of the switch, and thereby providing an annular torus or ring in which the movable body of mercury |03 is disposed. With this construction, rapid dissipation of heat from the metal envelope is provided due tothe large surface thereof in contact with the air. The

Vvretained body of mercury |04 in the undercut portion of the ceramic is of sufiicient volume due to its lying in an arcuate well to mask the face of the electrode 91 when the switch is tilted toward closed position. The straight through cylindrical opening |05 in the ceramic functions in the same manner as the opening 14 of Figure 3, and the operation of the switch through its various tilted positions is similar to that described in connection with Figures 3 to 6. However, by providing the movable body |03 in an arcuate position due to the reentrant portion |00 of Ythe envelope, stability is provided, insuring positive operating angles for the switch structure. The skirt 96 of the electrode 91 is contacted by a sucient volume of the retained body |04 to provide Y for small internal resistance in the switch, and the undercut 95 insures that the volume of mercury in the body |04 will be suicient to provide the double run feature, as well as cool operation and masking of the electrode face to insure mercury to mercury contact, and also to insure that making and breaking of the circuit will be occasioned over a portion of the ceramic removed from any metal parts of the switch structure.

In Figures 8 and 9 we have provided a modified ceramic structure adapt-ed to be incorporated in an envelope 10 corresponding to the envelope inherent stability, and by this construction it. is apparent that the retained body of mercury |20 will be retained in stable position relative to the space between the fingers I I9, as well as with respace to the space between the ends of the fingers and the face of the electrode I I8. The movable body of mercury |22 lying in the tubular end of the envelope is prevented by the shoulder H4 from dribbling through the opening ||5 until such time as a suflicient head is built up to insure a ow of mercury through the opening of sufficient section to insure positive contact. As this mercury ows through the opening H5, it contacts the portion |2| of the retained body of mercury lying between the lowermost fingers H9 of the ceramic, and the circuit is completed at this point and the movable body |22 never impinges upon any portion of the electrodeV H8.

It will of course be apparent that when the switch is tilted toward switch closing position, the retained body |20 rises in the space'between the lowermost fingers I |9 and also along the face of the electrode IIB, and consequently shields the electrode, as well as providing a stable mercury surface of considerable volume against which the lead edge of the mercury body |22 contacts. Thus, during making or breaking of the circuit through a switch of this type, any arcs will be formed adjacentthe ceramic surfaces and removed from the metal surfaces of the envelope.

In the embodiment of the invention shown in Figure 10, a switch corresponding more orless to the type shown in Figure 2 is provided, with the exception that the ceramic insert |25 is provided with the outwardly curved opening |26 in the center thereof leading to the cylindrical bore |21. This switch is not provided with an undercut but merely has a mercury retaining well |28 formed in the ceramic with the body of mercury |29 lying therein in contact with the flange portion |30 of the electrode |32 and with a movable body |33 adapted to move up over the surface |26 and through Vthe bore` |21 into contact with the body of mercury |29. The body of mercury |29 is of sufficient volume, however, to insure that when a-switch has been tilted to a point such that when the mercury |33 runs through the bore |21 the body of mercury |29 'l 'bore |21 which defines the well |28, andv consequently will be removed an appreciable distance from any of the metal parts of the switch.

The switch shown in Figure is provided with an insulating two piece case comprising a rst Such an insulating closure may be provided for all of the switches disclosed in the present application if so desired, and the defining junction between the pieces |34 and |35 may be suitably notched for leading out conductors |36 and |31 connected respectively to the shank of the electrode and to the metal retaining washer which is disposed in contact with the shell 10.

In the embodiment of the invention shown in Figure 11, a metal envelope |40 is provided having the radially enlarged cylindrical open end |42 within which is disposed the ceramic |43. This ceramic is provided with the frusto-conical bore |44 opening into a metal retaining well |45 deiined annularly by the metallic ange portion |46 of the electrode |41 and-carrying therein the retained body of mercury |48. A double flanged sealing member |49 is disposed in engagement with the radial outer faces of the electrode |41 and insert |43, the sealing means |49 having the forwardly extending peripheral flange |59 radially overlapping a portion of the ceramic insert |43 and having a rearwardly or outwardly extending skirt portion |52 which radially overlies a portion of the compression member |53. The shell is preferably beaded inwardly, as indicated at |54, to provide for radial compression of the sealing means intermediate the anges and |52, thereby insuring forcing of these flanges into tight compressive engagement between the internal walls of the extension |42 of the envelope and the ceramic pieces |43 and |53. This provides a very eiTective sealing means which cannot creep or ow during operation of the switch and 'which is augmented by the annular gasket seal |55 carried on the frusto-conical portion of the insert and engaging the shoulder portion |56 of the envelope. The electrode |41 has its radial inner face shielded by the ceramic |51 which is held in position by the ring |58 so that upon tilting of the switch, the radial face of the electrode is shielded against direct impingement ofA the movable body of mercury |59. Thusfa positive mercury to mercury contact is provided and the body of mercury |48 is of suiiicient volume to insure low resistance contact with the iiange portion |46 of the electrode, and also to produce the double run feature previously described.

In the modication of this structure s hown in Figure 12, the electrode |41' has the cera-mic disc |51 held in position by an internal bead |60 formed directly in the flange portion |46 of the cup-like electrode, whereby the use of an auxiliary retaining ring |58 is eliminated.

Considering now the form of the invention shown in Figure 13, a single diameter cupshaped metal shell or envelope |62 is provided which is adapted to receivethe insert |63, this insert being held axially in position within the open end of the envelope by providing an internal annular bead |64 providing a shoulder against which the ceramic is abutted. A frusto-conical gasket |65 which may be formed of any suitable material resistant to mercury is inserted between the inwardly extending end of the ceramic and the bead |64 toprovide 4sealing engagement at this point.' A cup-shaped electrode |66 has its llange portion |61 centered in the cylindrical bore formed in the outer end of the ceramic |63, and defines the annular surface of the mercury retaining well in which the retained body of mercury |68 is disposed. The insert |63 has the radial inner face |69 forming a shoulder against which the movable body of mercury |10 abuts to build up a suilicient head for rapid movement of the mercury |10 into the bore or passageway |12 of the ceramic, as described in connection with the shoulder 13 of Figure 3. The body of mercury |68 being closely confined at the inner end of theV passageway |12 rises along the inner face of the electrode |65 to shield the same from 'the `movable body of mercury |10 when contact Vis made.

With' this form of structure, it is apparent that the double drawing operations necessary for providing the two-diameter shells of previous -forms of the invention, is eliminated and the internal shoulder desired for seating the ceramic against axial inward movement is provided by the annular bead |64. The ceramic is sealed against outward movement by means of the resilient sealing gasket |13 and the compression member |14 in the same manner as describedin connection with Figures 1 and 2.

Considering now the modification of the invention shown in Figure 14, the switch envelope in this form of the invention is provided by using a straight tubular element |80, which is counterbored as at |82 t0 provide a shoulder for receiving the metal end plate |83 sealed in position by spinning over the end |84 of the tubular member. 'Ihe end plate |83 carries suitable tubulation |85 for iilling and evacuating the switch.

At its opposite end the member |80 is provided with a relatively long axially extending counterbored portion |86 forming the radial shoulder |81 adapted to receive the gasket |88 against which the ceramic insert |89 is disposed. The insert |89 is of simple form, having the radial internal shoulder portion |90 and the straight cylindrical bore |92 opening into a counterbored portion defined by the radial wall |93. A suitable cup-shaped electrode |94 is inserted into the counterbored-portion and centered therein, the ange |95 of the electrode forming the annular lining of the mercury well in which the retained body of mercury |96 is disposed. A suitable sealing gasket |91 engages the radial outer face of the electrode |94, and has the skirt portion |98 radially overlapping the electrode and tapered to radially overlie the tapered end portion |99 of the ceramic. A suitable compression member 206 engages the outer face of the gasket |91 to compress the same into sealing engagement, and also compress the gasket |88 into sealing engagement. The compression member 200 is held in position by the spun-over edge 202 of the counterbored portion of the envelope |80. The movable body of mercury 203 is adapted to be dammed up by ythe shoulder |90 until a sufficient head is built up to allow it to snap through th opening |92V into contact with the retained body |96 which, at the same time rises radially inwardly along the face of the electrode |94 to shield the same from direct impingement of mercury thereon.

It is to be understood that in the forms of the invention shown in Figures V2, V10, 11, 13 and 14, the ceramic, if desired, may bejprovided with an undercut portion similar to that shown in Figures 1, and 3 to 8 to provide the double run feature described in detail hereinbefore. Also, all forms of the invention may be enclosed within suitable insulating cases, as described in connection with Figure 10.

In Figure we have disclosed a modified form of switch construction in which the envelope 42 corresponding to the switch envelope shown in Figure 2 is provided in the enlarged open end thereof with the insulator 205, which insulator is provided with a tapered runway 206 of relatively short axial length which, at its inner end is provided with the radial step or shoulder '1 for a purpose to be hereinafter described. The insulator 205 is also provided with the annular recess or circuit 208 extending annularly about the runway 206 and having radial communication through the radial gap 209 with the small end of the runway. Disposed in a shouldered bore communicating with the recess 208 and the radial gap 209 to form a radial closure for the outer end of the insulator is an electrode disc 210 having the projecting shank 212 extending axially outwardly of the open end of the envelope. The disc 210 is adapted to receive a baille disc 213 which may comprise a metal such as tungsten, molybdenum, or any other similar metal having a far higher melting point, lower resistance, and higher conductivity than that of the iron forming the electrode. Molybdenum is preferred since it is slightly easier to machine and is less expensive. The disc is held in place by pressure between the ceramic shoulder and the iron electrode with the center ofV the disc being spot welded with nickel, as indicated at 214, tothe electrode face.

The axial extent of the radial gap 209 is what may be termed depth of electrode. The depth of the electrode in the form of the invention shown in Figure 15 has been determined by test` tobe most effective if maintained between -S and gse". The electrode and insulator are maintained in sealed relation in the end of the envelope by the sealing gasket 215 engaging the outer radial faces thereof and held in position by the compression member 21'1 corresponding to thev compression members 30 and 63.

In the operation of the switch shown in Figure l5, upon tilting of the switch envelope in a counter-clockwise direction as viewed in the drawings, the main body of mercury 218 rolls to the left and encounters the stop or shoulder 201 which prevents' its further movement until a sufficient head of mercury has been built up to run over the tapered runway 206. At the same time, the body of mercury 210 retained in the annular recess 203 and the radial gap 20S flows over the face of the disc 213, and consequently as the head of mercury from the body 218 breaks over the runway 206, it produces a positive mercury to mercury contact at the acute angle cutting edge 220 formed between the tapered runway 201i and the radial shoulder, which is spaced from the disc 213 to form the radial gap 209. Thus, there is no direct impingement of the mercury body 218 on the electrode disc. Similarly, when the circuit through the disc is to be broken, the switch is tilted in the opposite direction and the two bodies of mercury 218 and 219 run, respectively, out into the closed end of the shell 42 and into the recess 209, splitting over the cutting edge 220 whereby the movements of the two bodies of mercury are cumulative to increase the rate at which contact is broken in the switch and thereby minimize any arcing.

It is therefore vbelieved apparent that we have provided a novel type of mercury switch structure having certain features which insure positive repeatl performance and prevent any direct mercury to metal contact within the switch structure. At the same time, the structures are so designed as to insure that any-arcs occurring within the switch will be spaced away from the metal parts of the structure which are adequately shielded therefrom. Also, we have provided simplified sealing means, and in certain forms of the invention, simplied envelope structures for insuring economy in manufacture.

We are aware that various changes may be made in certain of the details herein shown and described, and therefore, do not intend to be limited except as defined by the scope and spirit of the appended claims.

We claim:

1. A mercury switch comprising a cup-shaped metal envelope having an enlarged cylindrical open end, a ceramic insert seated in said end having al large cylindrical bore extending into the outer end thereof, means at the end of saidenvelope locking said insert against axial movement, a coaxial small cylindrical bore formed in the inner end thereof, said ceramic insert having an intermediate cylindrical' flange portion between the bores providing for axial overlapping of said bores to define an annular axially extending recess about the inner bore, an electrode disc having a peripheral axial flange seated against axial movement in the outer end of lsaid large bore with the flange forming at least a portion of the outer annular wall of said recess, the end of said intermediate ceramic flange terminating axially inwardly of the electrode face to form a radial gap therebetween opening radially outwardly into said recess, a rst body of mercury in said envelope movable into said bore upon tilting of said switch in one direction, and a second body of mercury in said recess movable over the electrode face and said end of said bore upon said tilting to insure mercury to mercury contact.

2. The switch of claim 1 further characterized in that said recess defining means is provided.

wardly from said shoulder and terminating short I of the outer radial face thereof, an 'enlargedl borev in the outer end of said'insulator and axially overlapping said rst bore to provide an annular channel thereabout, a cup-shaped electrode closing the outer end of said enlarged bore and having the flange lying in said channel, bodies of mercury in said envelope and channel of substantially equal volume adapted to make and break contact over said terminating end of the first bore and axially spaced from said electrode l face, and axially spaced sealing means between said insulator and envelope.

4. A mercury switch comprising a cup-shaped metal envelope having an enlarged open end, an insulatorin said end having a radially inwardly directed shoulder at the inner end thereof, an

axial bore in said insulator extending outwardly from said shoulder and terminating short of the outer radial face thereof, an enlarged bore in the outer end of said insulator and axially overlapping said flrst bore to provide an annular channel thereabout, a cup-shaped electrode closing the outer end of said enlarged bore and having the llange lying in said channel, bodies of mercury in said envelope and channel of substantially equal volume adapted to make and break contact over said terminating end of the rst bore and axially spaced from said electrode face, and a baffle disc lying yover the face of said electrode within said flange.

5. A mercury switch comprising a cup-shaped metal envelope having an enlarged open end, an insulator in said end having a radially inwardly directed shoulder at the inner end thereof, an axial bore in said insulator' extending outwardly from said shoulder and terminating short of the outer radial face thereof, an enlarged bore in the outer end of said insulator and axially overlapping said rst 'bore to provide an annular channel thereabout, a cup-shaped electrode closing the outer end of said enlarged bore and having the flange lying in said channel, bodies of mercury in said envelope and channel of substantially equal volume adapted to make and break contact over said terminating end of the rst bore and axially spaced from said electrode face, and an insulating disc secured over the face of said electrode.

6; A mercury switch comprising avcup-shaped metal envelope having an enlarged open end, an

insulator in said end'having a radially inwardly directed shoulder at the inner end thereof, an axial bore in said insulator extending outwardly from said shoulder and terminating short of the y outer radial face thereof, an enlarged bore in the outer end of said insulator and axially overlapping said iirst bore to provide an annular channel thereabout, a cup-shaped electrode .closing the outer end of said enlarged bore and having the flange lying in said channel, bodies of mercury in said envelope and channel of substantially equal volume-adapted to make and .break contact over said terminating end of the first bore and axially spaced from said electrode face, and a disc of a metal of the group consisting of tungsten, molybdenum or tantalum lying over vthe face of said electrode.

7. The switch of claim 3 further characterized in that said insulator has an annular groove formed in the lateral surface thereof adjacent the inner end adapted to support one of said sealing means. p

8. A mercury switch comprising a cup-shaped metal envelope having an insulator secured in the open end thereof provided with an axial bore, a cup-shaped electrode carried in the outer end of said insulator closing said bore, a resilient sealing disc having opposed axial flanges at the periphery thereof extending over the outer radial faces of said insulator with one of said flanges radially overlapping said insulator, a compres- SOII member engaging the outer face of said disc, the other of said flanges radially overlapping said compression member, and an annular bead formed in said envelope intermediate said flanges.

9. In combination, a cup-shaped metal envelope having an annular internal bead formed adjacent the open end thereof, an insulator in said end, sealing means between said bead and insulator, an axial bore in said insulator, an electrode seated in the outer end of said insulator closing said bore, sealing means engaging the outer face of said electrode and insulator and radially overlapping said insulator, and means at the end of said envelope for axially compressing both said sealing means.

10. A mercury switch comprising an enclosing metal envelope having an insulator in one end thereof carrying an electrode, said insulator having-means for retaining a body of mercury in contact with said electrode throughout normal operating movement of the switch, a second body of mercuryvin the envelope, said bodies making and breaking contact over a portion of said insualtor spaced from said electrode, and a central axially extending reentrant portion in one end of said envelope forming an annular recess exposedV to outside air and terminating at its inner end adjacent said portion of said insulator.

1l. A mercury switch comprising a cup-shaped metal envelope having an enlarged open end dened by a radial shoulder, an insulator in said end seated against said shoulder, an annular groove in the face of said insulator engaging said shoulder, sealing means in said groove, an electrode carried by and closing the outer end of sai-d insulator, a bore in said insulator providing communication between said envelope and electrode, sealing means engaging the outer radial faces of said electrode and insulator, and means for axially compressing both said sealing means.

12, The switch of claim 11 further character- 'Vized by the provision of an axially directed reentrant portion in said envelope at the junction of said body portion and shoulder adjacent said rst named sealing means and extending to a point adjacent said bore.

13. The combination of claim 11 wherein said insulator has an annular recess radially spaced from said bore and opening toward said electrode,

a body of mercury confined in said recess, and

a second body of mercury movable through said bore to makeV and break contact with said first body of mercury,

HERBERT E. BUCKLEN. UNO C. HEDIN. 

